trait Into_<T> {
    fn into(self) -> T;
}

impl Into_<i32> for i8 {
    fn into(self) -> i32 { self as i32 }
}

impl Into_<i32> for bool {
    fn into(self) -> i32 { self as i32 }
}

fn abs_i32<T>(a: T) -> i32
    where T: Into_<i32>
{
    a.into().abs()
}

fn main() {
    println!("{} {}", abs_i32(true), abs_i32(false));
    println!("{}", abs_i32(-100i8));

//    1i32 as bool;
    true as i32;
}